Research On Working Characteristics Of Horizontally Loaded Inclined-Straight Pile Group Foundations

Inclined pile refers to the pile foundation with a certain inclination angle,which is often used to resist large horizontal load.At present,the quantitative relationship between the layout of inclined piles,the inclination of pile body and the bearing capacity has not formed a unified understanding,and its mechanical characteristics need to be further studied and discussed.Based on the research results of domestic and foreign scholars on inclined piles,the horizontal bearing characteristics of inclined straight composite pile groups are analyzed by the combination of model test and numerical simulation.The main research contents and results are as follows:（1）The horizontal static load model tests of inclined single pile with different inclination and inclination are carried out,and the changes of horizontal displacement of bearing platform,internal force of pile body and earth pressure on pile side are analyzed.The results show that the horizontal bearing capacity of positive inclined pile,vertical pile and negative inclined pile decreases;The greater the inclination of the pile body,the greater the bearing capacity of the positive inclined pile and the smaller the negative inclined pile.With the increase of load,the position of maximum bending moment and maximum negative shear force of negative inclined pile is deeper than that of positive inclined pile.The shallow soil in front of the pile reaches the ultimate resistance and fails before the positive inclined pile,and the plastic zone expands to the deep layer in advance.（2）The horizontal static load model test of inclined straight pile group is carried out to study the influence of setting inclined piles with different inclination and inclination,pre applying vertical load and increasing length diameter ratio under constant vertical load on its horizontal bearing characteristics.The results show that under the same loading condition,the horizontal bearing performance of inclined straight pile group is better than that of vertical pile group,and the greater the inclination,the greater the bearing capacity of pile group in the same combination form.When only horizontal load is applied,the bearing capacity of positive inclined pile group is greater than that of negative inclined pile group with the same inclination;The vertical load reduces the horizontal bearing capacity of positive inclined pile group and improves the horizontal bearing capacity of negative inclined pile group,and the greater the slope is,the more obvious the change is.Properly increasing the length diameter ratio reduces the pile bending moment,shear force and earth pressure in front of the pile,and improves the working performance of pile groups.（3）Combined with the field test parameters,ABAQUS finite element software is used to simulate the horizontal loaded inclined single pile and inclined straight pile group,analyze the pile-soil displacement and soil plastic deformation under different simulation conditions,and better verify the relevant laws of model test in this paper.（4）The single-pile simulation results show that the positive-inclined pile under the horizontal force exerts a downward pressure on the soil in front of the pile,which improves the soil strength;the negative-inclined pile lifts the soil in front of the pile and reduces the soil strength.The vertical force strengthens the extrusion effect of the positive-inclined pile on the soil in front of the pile under the horizontal force,which increases the plastic zone;Development of the plastic zone.（5）The simulation results of the pile group show that when only the horizontal load is applied,the pile uplift amplitude of the negative-inclined pile group is larger,and the shallow soil produces more uplift displacement,which is more prone to damage than the positive-inclined pile group.The pre-applied vertical load increases the horizontal displacement of the horizontally loaded slanted pile group,and the greater the vertical load and the inclination angle,the more obvious the increase;the appropriate vertical load reduces the horizontally loaded slanted pile group horizontal displacement,However,if the vertical load is too large,the displacement will increase instead,and there is an optimal vertical load value that can maximize its horizontal bearing capacity.After the pile length is properly increased,the horizontal displacement of each pile group decreases greatly,and the plastic zone of the soil around the pile decreases accordingly.